1. Field of Invention
The invention relates, generally, to an electronic control unit and, more specifically, to such a unit employed with lighting equipment of a motor vehicle.
2. Description of Related Art
An electronic control unit, particularly in the area of motor vehicles, has to be placed in a control-unit box for protection from dirt, moisture, and outside mechanical effects. To improve “EMC” compatibility, this box consists partly of metal. This often leads to a conflict between a most compact geometry of the control unit, on the one hand, and prevention of heat accumulation in the inside of the box, on the other hand.
Use of flexible substrates for conductor-board materials is known from various applications. A conductor board is used, on the one hand, as a carrier and for mechanical fixture and, on the other hand, for applying electronic contact for electronic components. Nearly every electronic appliance—in particular, an electronic control unit—consists of one or more conductor boards. Stiff or inflexible conductor boards are used most cases.
As an alternative to inflexible conductor boards, it is more and more common to use thin, flexible conductor boards—for example, on a foundation of polyimide foils. Those so-called “flex circuits” can be re-shaped, for example, by folding of bending so that they fit in the narrowest structures, such as in cameras or camcorders. Yet, disadvantages of such flexible conductor boards are fairly high costs, poor thermal conductivity of heat produced by electrical components during operation, and missing mechanical-form stability of the conductor boards. Therefore, populating conductor foil using placement machines is made difficult, and it is very complicated to achieve mechanical stability of the assembled conductor boards, e.g., in the control-unit box.
In case there is need for only one part of the conductor board to be flexible (e.g., for making it possible to mount the board in very cramped conditions), there is a possibility to reduce thickness of a populated conductor board—e.g., by milling. A thinned area can, thus, be bent a few times. This technique leads to so-called “rigid-flex boards.” A disadvantage of this technology is that each bending edge allows only for a one-dimensional re-shaping. Further, in cramped-space conditions, a fairly large bending radius is particularly disadvantageous as a lost populating area since it is only possible to populate components outside of a bending area.
Finally, there is a known construction to prevent the disadvantages when using known flex boards in that the assembled flexible conductor foil is fixed onto a solid basic board as foundation—e.g., by gluing these two together. However, disadvantageously, to make sure that there is no inappropriate material strain resulting from differing bending radii, it is necessary to suspend the solid basic board in the bending area. To ensure mechanical stability, it is necessary to strengthen construction with a further element. Further, assembly of this flexible conductor board with its lacking form stability proves to be complicated. Finally, fixing of the populated conductor board on the basic body is elaborate and complicated. The danger exists that some electronic components might be destroyed or loosen from the board during the process of fastening.
Due to thermal requirements and conditions while using electronic components, it is commonly necessary to cool the electronic components in a suitable way. This can be achieved by a mechanical connection to a cooling element, which will absorb heat and can dissipate it to a surrounding area.
Thus, there is a need in the related art for a unit that is made-up of a conductor board and basic body for a control unit and omits the disadvantages described above. More specifically, there is a need in the related art for such a unit that allows an optimal connection between heat-emitting components and cooling elements when using flexible conductor boards. There is a need in the related art for such a unit that also maximizes space and area on the conductor board available for arranging electric and electronic components in the control unit while achieving an improved thermal conductivity of components and three dimensionally shaped flexible conductor boards. There is a need in the related art for such a unit also of which area for populating electronic components is maximized while providing enough stability for surface-mounted components during assembly or using the control unit.